There are several places on the fuselage where the interaction of components require the use of some kind of filler to create a solid foundation for fabric covering. Front left AL panel and carbon fiber intersection adjacent to fuel selector/Rear Fuel Drain area/Longeron and Alloy Tubing both sides of rear fuselage to name a few.
CC use Bondi in the videos, but Polyfiber advise "No" because of shrinkage and later possible de-lamination of the fiber.
Some suggest the application of anti-chafe tape in susceptible areas to cover the filler before covering will work.
Others say an epoxy filler? is the only answer.
What works?